Objective: To investigate the factors affecting the sample satisfaction rate of ultrasound-guided fine needle aspiration biopsy (US-FNAB) of thyroid nodules, and the influences of different gauges of puncture needle and different types of vascularity of the thyroid nodule on the sample satisfaction rate. 
Methods: The clinical data of 310 patients with thyroid nodules (a total of 337 nodules) undergoing US-FNAB from June 2015 to September 2017 were analyzed. The relations of sample satisfaction rate with puncture needle gauge and type of vascularity of thyroid nodule as well as other factors were analyzed, and the differences in sample satisfaction rate of thyroid nodules with different vascularity using different gauges of puncture needle were also compared.
Results: Among the 337 samples of nodules, 295 samples (87.5%) were satisfying, and 42 samples (12.5%) were not satisfying. Results of statistical analysis showed that the unsatisfaction rate in hypervascular nodule was significantly increased (P=0.001), but the puncture needle gauge and all other factors had no significant relation with sample satisfaction rate (all P>0.05). In the 161 samples of hypervascular nodule, the sample needles satisfaction rates by using 23G and 25G needles were 73.3% and 88.4% (P<0.05); in the 176 samples of hypovascular nodule, the satisfaction rates by using 23G and 25G needles were 96.8% and 88.9% (P<0.05). In the 170 samples drawn by 23G needle, the satisfaction rates for hypervascular and hypovascular nodule were 73.3% and 96.8%; in the 167 samples drawn by 25G needle, the satisfaction rates for hypervascular and hypovascular nodule were 88.4% and 88.9% (P>0.05).
Conclusion: The hypervascular nodule is more likely to result in unsatisfied sample. The needle gauge has no obvious influence on the sample satisfaction rate of FNAB, and both 23G and 25G needles can meet the requirement of US-FNAB. However, the 23G needle is more suitable for the hypovascular nodules, and the 25G needle is more suitable for the hypervascular nodules.